A NEW GENETIC TYPE OF HYDROTHERMAL MAGNETITE MINERALIZATION IN DEPOSITS OF THE ANGARA PROVINCE

Abstract

A study of mineral associations produced in the third stage of the mineragenesis suggest that the halite is inseparably connected with sulfates in the halite-sulfate process and provides unambiguous proof that magnetite generation can be produced by this process. The magnetite of the halide-sulfate process is of stoichiometric composition, always contains microinclusions of other minerals, and has an Ni/Co ratio of less than 1. These data cast significant new light on many important aspects of the ore genesis in the Angara province. They are inconsistent with the idea that the commercial magnetite ores at the bases of the cup-like depressions are of exclusively sedimentary origin, since they fully confirm V.A. Vakhrushev's data indicating the occurrence of 'hydrothermal-metasomatic' magnetite in them; they unambiguously specify its position in the mineragenesis sequence and refute the theory that commercial halite-magnetite ores result from replacement of magnetite by halite-containing sedimentary sequences. Rather, halite is one of the last minerals to crystallize in every stage of the halide-sulfate process. This is the first time that magnetite generation association with the halide-sulfate hydrothermal process has been identified.